Remove branch arg from git docs.

The "branch" arg doesn't work, users should use "version" instead
for specifying branches.

rst/modules.rst

@@ -302,11 +302,7 @@ Deploys software (or files) from git checkouts.
 *version*:
 
 * What version to check out -- either the git SHA, the literal string
-  ``HEAD``, or a tag name.
-
-*branch*:
-
-* (new in 0.4) Which branch name to checkout.  Defaults to 'master'.
+  ``HEAD``, branch name, or a tag name.
 
 Example action from Ansible :doc:`playbooks`::